Abstract Acceleration in Linear relation analysis (extended version)

Linear relation analysis is a classical abstract interpretation based on an over-approximation of reachable numerical states of a program by convex polyhedra. Since it works with a lattice of infinite height, it makes use of a widening operator to enforce the convergence of fixed point computations. Abstract acceleration is a method that computes the precise abstract effect of loops wherever possible and uses widening in the general case. Thus, it improves both the precision and the efficiency of the analysis. This research report gives a comprehensive tutorial on abstract acceleration: its origins in Presburger-based acceleration including new insights w.r.t. the linear accelerability of linear transformations, methods for simple and nested loops, recent extensions, tools and applications, and a detailed discussion of related methods and future perspectives. This is the long version of a paper under submission

Cell morphing: from array programs to array-free Horn clauses

International audienceAutomatically verifying safety properties of programs is hard.Many approaches exist for verifying programs operating on Boolean and integer values (e.g. abstract interpretation, counterexample-guided abstraction refinement using interpolants), but transposing them to array properties has been fraught with difficulties.Our work addresses that issue with a powerful and flexible abstractionthat morphes concrete array cells into a finite set of abstractones. This abstraction is parametric both in precision and in theback-end analysis used.From our programs with arrays, we generate nonlinear Horn clauses overscalar variables only, in a common format with clear and unambiguouslogical semantics, for which there exist several solvers. We thusavoid the use of solvers operating over arrays, which are still veryimmature.Experiments with our prototype VAPHOR show that this approach can proveautomatically and without user annotationsthe functional correctness of several classical examples, including \emph{selection sort}, \emph{bubble sort}, \emph{insertion sort}, as well as examples from literature on array analysis

Quantity of Resource Properties Expression and Runtime Assurance for Embedded Systems

International audienceRecent work on component-based software design has proved the need of resource-accurate development of embedded software. In the more specific cases of mobile systems, the developer also needs tools to facilitate the adaptation of functionalities to resources (lack of memory or bandwidth, \etc), and also to evaluate the performance w.r.t. the resource issues . As we want to design and develop at the same time the application and its resource controllers, we chose to use Qinna, which was designed to manage resource issues (specification, contractualization, management) during the development process of such an application. We propose a complete formalization of the resource constraints specification, through the use of a variant of the event-based logics, MEDL and PEDL introduced in \cite{lee99runtime}. Qinna then automatically performs the runtime resource assurance. We illustrate this work in a case study

Verifying Programs with Arrays and Lists

Automatically verifying safety properties of programs is a tough problem that has been tackled using many different approaches: rewriting systems, abstract interpretation, SMT solving,. .. Most techniques restrict themselves to programs operating on boolean and integer values and transposing them to infinite data structures such as arrays has not yet been satisfyingly achieved. Recent work in Monniaux and Gonnord [2016] suggests the use of abstract interpretation to transpose programs containing arrays into Horn clauses that do not contain arrays. The major innovation of their work is that they use Horn clauses which are more general than programs, to obtain better results. In this work, we first set the work of Monniaux and Gonnord in a more general framework that allows us to extend their abstractions, simplify the expressions they generate, and analyze the precision of their abstraction. Finally we extend their abstractions so that we can the analyze lists and experiments show that we succeed to analyze several classical examples, including sorting algorithms

Estimation of Parallel Complexity with Rewriting Techniques

International audienceWe show how monotone interpretations – a termination analysis technique for term rewritingsystems – can be used to assess the inherent parallelism of recursive programs manipulatinginductive data structures. As a side effect, we show how monotone interpretations specify aparallel execution order, and how our approach extends naturally affine scheduling – a powerfulanalysis used in parallelising compilers – to recursive programs. This work opens new perspectivesin automatic parallelisation

On Complexity Bounds and Confluence of Parallel Term Rewriting

We revisit parallel-innermost term rewriting as a model of parallel computation on inductive data structures and provide a corresponding notion of runtime complexity parametric in the size of the start term. We propose automatic techniques to derive both upper and lower bounds on parallel complexity of rewriting that enable a direct reuse of existing techniques for sequential complexity. Our approach to find lower bounds requires confluence of the parallel-innermost rewrite relation, thus we also provide effective sufficient criteria for proving confluence. The applicability and the precision of the method are demonstrated by the relatively light effort in extending the program analysis tool AProVE and by experiments on numerous benchmarks from the literature.Comment: Under submission to Fundamenta Informaticae. arXiv admin note: substantial text overlap with arXiv:2208.0100

Modular termination of C programs

In this paper we describe a general method to prove termination of C programs in a scalable and modular way. The program to analyse is reduced to the smallest relevant subset through a termination-specific slicing technique. Then, the program is divided into pieces of code that are analysed separately, thanks to an external engine for termination. The result is implemented in the prototype \stoptool over our previous toolsuite WTC [compsys-termination-sas10] and preliminary results shows the feasibility of the method

Enhancing the Compilation of Synchronous Dataflow Programs with a Combined Numerical-Boolean Abstraction

RR version = http://hal.inria.fr/hal-00780521/enInternational audienceIn this paper, we propose an enhancement of the compilation of synchronous programs with a combined numerical-Boolean abstraction. While our approach applies to synchronous dataflow languages in general, here, we consider the SIGNAL language for illustration. In the new abstraction, every signal in a program is associated with a pair of the form ( clock, value ), where clock is a Boolean function and value is a Boolean or numeric function. Given the performance level reached by recent progress in Satisfiability Modulo Theory (SMT), we use an SMT solver to reason on this abstraction. Through sample examples, we show how our solution is used to determine absence of reaction captured by empty clocks; mutual exclusion captured by two or more clocks whose associated signals never occur at the same time; or hierarchical control of component activations via clock inclusion. We also show that the analysis improves the quality of the code generated automatically by a compiler, e.g., a code with smaller footprint, or a code executed more efficiently thanks to optimizations enabled by the new abstraction. The implementation of the whole approach includes a translator of synchronous programs towards the standard input format of SMT solvers, and an ad hoc SMT solver that integrates advanced functionalities to cope with the issues of interest in this wor

Analysing Parallel Complexity of Term Rewriting

We revisit parallel-innermost term rewriting as a model of parallel computation on inductive data structures and provide a corresponding notion of runtime complexity parametric in the size of the start term. We propose automatic techniques to derive both upper and lower bounds on parallel complexity of rewriting that enable a direct reuse of existing techniques for sequential complexity. The applicability and the precision of the method are demonstrated by the relatively light effort in extending the program analysis tool AProVE and by experiments on numerous benchmarks from the literature.Comment: Extended authors' accepted manuscript for a paper accepted for publication in the Proceedings of the 32nd International Symposium on Logic-based Program Synthesis and Transformation (LOPSTR 2022). 27 page